Abstract
Glutamate uptake by high affinity glutamate transporters is essential for preventing excitotoxicity and maintaining normal synaptic function. We have discovered a novel role for presenilin-1 (PS1) as a regulator of glutamate transport. PS1-deficient neurons showed a decrease in glutamate uptake of approximately 50% compared to wild-type neurons. Gamma-secretase inhibitor treatment mimicked the effects of PS1 deficiency on glutamate uptake. PS1 loss-of-function, accomplished by PS1 deficiency or gamma-secretase inhibitor treatment, caused a corresponding decrease in cell surface expression of the neuronal glutamate transporter, EAAC1. PS1 deficiency is known to reduce intracellular calcium stores. To explore the possibility that PS1 influences glutamate uptake via regulation of intracellular calcium stores, we examined the effects of treating neurons with caffeine, thapsigargin, and SKF-96365. These compounds depleted intracellular calcium stores by distinct means. Nonetheless, each treatment mimicked PS1 loss-of-function by impairing glutamate uptake and reducing EAAC1 expression at the cell surface. Blockade of voltage-gated calcium channels, activation and inhibition of protein kinase C (PKC), and protein kinase A (PKA) all had no effect on glutamate uptake in neurons. Taken together, these findings indicate that PS1 and intracellular calcium stores may play a significant role in regulating glutamate uptake and therefore may be important in limiting glutamate toxicity in the brain.
Publication types
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Transport System X-AG / metabolism
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Amyloid Precursor Protein Secretases
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Animals
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Aspartic Acid Endopeptidases
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Biological Transport / drug effects
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Caffeine / pharmacology
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Calcium / metabolism*
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Calcium Channel Blockers / pharmacology
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Cells, Cultured
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Cyclic AMP-Dependent Protein Kinases / drug effects
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Cyclic AMP-Dependent Protein Kinases / metabolism
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Dose-Response Relationship, Drug
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Endopeptidases / drug effects
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Enzyme Activators / pharmacology
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Enzyme Inhibitors / pharmacology
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Excitatory Amino Acid Transporter 3
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Glutamate Plasma Membrane Transport Proteins
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Glutamic Acid / metabolism*
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Glutamic Acid / pharmacokinetics
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Imidazoles / pharmacology
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Intracellular Fluid / metabolism*
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Kainic Acid / analogs & derivatives*
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Kainic Acid / pharmacology
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Membrane Proteins / deficiency
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Membrane Proteins / genetics
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Membrane Proteins / physiology*
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Mice
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Mice, Knockout
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Neurons / cytology
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Neurons / drug effects
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Neurons / metabolism*
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Presenilin-1
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Protein Kinase C / drug effects
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Protein Kinase C / metabolism
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Symporters / metabolism
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Thapsigargin / pharmacology
Substances
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Amino Acid Transport System X-AG
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Calcium Channel Blockers
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Enzyme Activators
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Enzyme Inhibitors
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Excitatory Amino Acid Transporter 3
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Glutamate Plasma Membrane Transport Proteins
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Imidazoles
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Membrane Proteins
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Presenilin-1
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Slc1a1 protein, mouse
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Symporters
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Caffeine
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Glutamic Acid
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dihydrokainic acid
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Thapsigargin
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Cyclic AMP-Dependent Protein Kinases
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Protein Kinase C
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Amyloid Precursor Protein Secretases
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Endopeptidases
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Aspartic Acid Endopeptidases
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Bace1 protein, mouse
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1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole
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Kainic Acid
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Calcium